.____ frightened me was a loud crash from the next room.A] That [B] Why [C] What [D] How

.____ frightened me was a loud crash from the next room.A] That [B] Why [C] What [D] How

选择C
这是个主语从句,主语从句缺少主语.只能用what

c 引导主语从句

C

选C。